The rolling bearing cage is provided to keep the rolling bodies, usually balls according to the present invention, at a uniform spacing with respect to one another. According to the prior art, corresponding cages can be formed as an open or closed ring or from a multiplicity of segments.
The rolling bearing cage should be suitable in particular for large rolling bearings, such that the diameter of the cage is then at least one meter. In the case of large rolling bearings, there are restrictions with regard to the production of suitable rolling bearing cages on account of the size alone. Thus, injection-molded plastics cages are uneconomical in view of the costs for corresponding injection molds and the usual quantity of large rolling bearings. Although cages made from simple plastics strips are cost-effective to manufacture, they have only very low strength in the circumferential direction and are therefore not suitable for many applications. In this case, it should also be borne in mind that, particularly in the case of large rolling bearings, subsequent replacement of the bearing is associated in part with very high costs and very great effort.
DE 30 41 355 A1 discloses a cage for a conventional ball bearing having an inner race, an outer race and a plurality of balls arranged in between, wherein the cage is formed from two sheet metal parts which each have a coating of plastics material. The production of such a cage formed from two shaped and coated sheet metal strips is complicated and not suitable for large rolling bearings. Since the coating is initially applied to the punched parts in an electrostatic process or a fluid bed process, transitions at which an increased risk of damage can occur remain after the punched parts have been connected. Provided as the coating is a thermoplastic, in particular polyamide, in order to protect the contact surfaces of the cage with the balls and the inner and the outer race from wear and to reduce the coefficient of friction.
DE 197 51 003 A1 discloses a process and an apparatus for coating workpieces with a pulverulent, granular, liquid or pasty coating medium, wherein the coating medium is applied in a fluidized bed. Excess coating medium is removed prior to the final melting and adhering to the workpiece. Therefore, a complicated procedure is necessary. The process and the apparatus described are provided in particular for endless workpieces which are then subsequently brought into their final form.